Cannot backup from Proxmox to PBS

Hello everybody,

I am trying to setup PBS, which I have as a container inside Proxmox (I know that separate hardware would be better, I want to store my backups on the cloud and one day I will migrate it to separate hardware). I created a datastore in PBS and connected it to a mounted directory, specifically to an storage box in the cloud. After successfully doing so, I could also see the correct storage size of the datastore, and I can also write from PBS to my remote storage without problems. I then added the datastore in Proxmox as a new storage but unfortunately i get this error when trying to backup a random container. I saw that some file (mnt/storagebox/.chunks/6682/668294e80f80d1950a107ac4828eb647a32dad7ae240c8203b65569055e572ef.tmp_XXXXXX" failed: ENOENT: No such file or directory) is missing? But i figured the solution cannot be to manually create such directories / files in my mounted storagebox directory.

The other thing I thought was that it maybe has to do something about permissions. For example, I had to first create the datastore in PBS and then mount my cloud storage box. If I did it in the other way around, i got "Permission denied" as an error when trying to create a datastore with the mounted path as directory.

Any help would be much appreciated.

INFO: starting new backup job: vzdump 105 --notification-mode notification-system --node pve --remove 0 --mode snapshot --storage pbs-hetzner --notes-template '{{guestname}}'
INFO: Starting Backup of VM 105 (lxc)
INFO: Backup started at 2026-01-27 12:11:19
INFO: status = running
INFO: CT Name: Nextcloud
INFO: including mount point rootfs ('/') in backup
INFO: including mount point mp0 ('/nextcloud-data') in backup
INFO: backup mode: snapshot
INFO: ionice priority: 7
INFO: suspend vm to make snapshot
INFO: create storage snapshot 'vzdump'
INFO: resume vm
INFO: guest is online again after 1 seconds
INFO: creating Proxmox Backup Server archive 'ct/105/2026-01-27T11:11:19Z'
INFO: set max number of entries in memory for file-based backups to 1048576
INFO: run: lxc-usernsexec -m u:0:100000:65536 -m g:0:100000:65536 -- /usr/bin/proxmox-backup-client backup --crypt-mode=encrypt --keyfd=15 pct.conf:/var/tmp/vzdumptmp3281013_105/etc/vzdump/pct.conf root.pxar:/mnt/vzsnap0 --include-dev /mnt/vzsnap0/./ --include-dev /mnt/vzsnap0/./nextcloud-data --skip-lost-and-found --exclude=/tmp/?* --exclude=/var/tmp/?* --exclude=/var/run/?*.pid --backup-type ct --backup-id 105 --backup-time 1769512279 --entries-max 1048576 --repository root@pam@192.168.2.106:hetzner-storagebox
INFO: Starting backup: ct/105/2026-01-27T11:11:19Z
INFO: Client name: pve
INFO: Starting backup protocol: Tue Jan 27 12:11:20 2026
INFO: Using encryption key from file descriptor..
INFO: Encryption key fingerprint: 10f:qw:98:r1:m7:ca:52:r1
INFO: No previous manifest available.
INFO: Upload config file '/var/tmp/vzdumptmp3281013_105/etc/vzdump/pct.conf' to 'root@pam@192.168.2.106:8007:hetzner-storagebox' as pct.conf.blob
INFO: Upload directory '/mnt/vzsnap0' to 'root@pam@192.168.2.106:8007:hetzner-storagebox' as root.pxar.didx
INFO: unclosed encoder dropped
INFO: closed encoder dropped with state
INFO: unfinished encoder state dropped
INFO: finished encoder state with errors
INFO: catalog upload error - channel closed
INFO: Error: inserting chunk on store 'hetzner-storagebox' failed for 668294e80f80d1950a107ac4828eb647a32dad7ae240c8203b65569055e572ef - mkstemp "/mnt/storagebox/.chunks/6682/668294e80f80d1950a107ac4828eb647a32dad7ae240c8203b65569055e572ef.tmp_XXXXXX" failed: ENOENT: No such file or directory
INFO: cleanup temporary 'vzdump' snapshot
ERROR: Backup of VM 105 failed - command 'lxc-usernsexec -m u:0:100000:65536 -m g:0:100000:65536 -- /usr/bin/proxmox-backup-client backup '--crypt-mode=encrypt' '--keyfd=15' pct.conf:/var/tmp/vzdumptmp3281013_105/etc/vzdump/pct.conf root.pxar:/mnt/vzsnap0 --include-dev /mnt/vzsnap0/./ --include-dev /mnt/vzsnap0/./nextcloud-data --skip-lost-and-found '--exclude=/tmp/?*' '--exclude=/var/tmp/?*' '--exclude=/var/run/?*.pid' --backup-type ct --backup-id 105 --backup-time 1769512279 --entries-max 1048576 --repository root@pam@192.168.2.106:hetzner-storagebox' failed: exit code 255
INFO: Failed at 2026-01-27 12:11:22
INFO: Backup job finished with errors
INFO: notified via target `mail-to-root`
TASK ERROR: job errors